I'd like to review our dev setup for 4.0-beta. Some of the things already have their own issues but it might be easier to do all of the updates in a fewer number of PRs (probably still multiple).

• Update VP project (PHP). Done mostly in Dockerized dev setup, Dockerized dev setup #1227.
• Update frontend project (TypeScript / React): PR 1213 frontend dependencies and other updates #1214
• npm -> Yarn won't happen, see npm -> Yarn #1142 (comment)
  • Revert parts of 1213 frontend dependencies and other updates #1214 in a separate PR; frontend already switched to Yarn. done in Dockerized dev setup Dockerized dev setup #1227
• Update .idea template files Update .idea template files #1144
  • This has also happened in Dockerized dev setup Dockerized dev setup #1227
• PhpStorm inspections done in Dockerized dev setup Dockerized dev setup #1227
• Adopt PHPStan see separate issue Adopt PHPStan #1210
• Review and update Dev-Setup.md -> part of Dockerized dev setup Dockerized dev setup #1227
• Gulp -> npm scripts? Won't happen at this point.